Space and astronomy news
The tiny hopping-robot MASCOT completed its 17 hour mission on the asteroid Ryugu in early October. Now the German Aerospace Center (DLR) has released an image of MASCOT’s path across the asteroid. Surprised by what MASCOT found on the surface, they’ve named the landing spot “Alice’s Wonderland.”
Continue reading “The Path that MASCOT Took Across Asteroid Ryugu During its 17 Hours of Life”
Earlier this week asteroid Ryugu had a visitor. The Mobile Asteroid Surface Scout (MASCOT) landed on Ryugu on October 3rd after it was successfully deployed from the Japanese Hayabusa2 space probe. The little hopping robot’s visit was brief however, and it stopped functioning on Oct. 4th.
Continue reading “A German-French Hopping Robot Just Landed on the Surface of Asteroid Ryugu”
Within near-Earth space, there are over 18,000 asteroids whose orbit occasionally brings them close to Earth. Over the course of millions of years, some of these Near-Earth Objects (NEOs) – which range from a few meters to tens of kilometers in diameter – may even collide with Earth. It is for this reason that the ESA and other space agencies around the world are engaged in coordinated efforts to routinely monitor larger NEOs and track their orbits.
In addition, NASA and other space agencies have been developing counter-measures in case any of these objects stray too close to our planet in the future. One proposal is NASA’s Double Asteroid Redirection Test (DART), the world’s first spacecraft specifically designed to deflect incoming asteroids. This spacecraft recently moved into the final design and assembly phase and will launch to space in the next few years.
Welcome to the 575th Carnival of Space! The Carnival is a community of space science and astronomy writers and bloggers, who submit their best work each week for your benefit. We have a fantastic roundup today including news from the IAU, so now, on to this week’s worth of stories!
Continue reading “Carnival of Space #575”
The Hubble Space Telescope is the oldest space telescope in operation, having spent the past twenty-eight years in orbit. Nevertheless, this mission is still hard at work revealing things about our Solar System, neighboring exoplanets, and some of the farthest reaches of the Universe. And every so often, it also captures an image that happens to turn up something interesting and unexpected.
Recently, while conducting a study of Abell 370, a galaxy cluster located approximately four billion light-years away in the constellation Cetus (the Sea Monster), Hubble managed to spot something in foreground. While observing this collection of several hundred galaxiess, the image was photobombed by 22 asteroids whose tails created streaks that looked like background astronomical phenomena.
The study was part of the Frontier Fields program, where Hubble has captured images of some of the earliest galaxies in the Universe (aka. “relic galaxies”) in order to determine how it evolved over time. The position of this asteroid field is near the ecliptic (the plane of our Solar System) where most asteroids reside, which is why Hubble astronomers saw so many crossings.
In the past, Hubble has recorded many instances of asteroid trails when conducting observations along a line-of-sight near the plane of our Solar System. In this case, the Near-Earth Asteroids (NEAs) – which orbit Earth at an average distance of about 260 million km (161.5 million mi) – were previously undetected due to their faintness. But thanks to the images taken by Hubble, scientists were able to identify them manually based on their motion.
Of the 22 asteroids, five were identified as unique objects. The image was assembled from several exposures taken in visible and infrared light, which was first released on November 6th, 2017. The image was prepared in honor of “Asteroid Day”, a global annual event that takes place every June 30th to raise awareness about asteroids and what can be done to protect Earth from a possible impact.
The day falls on the anniversary of the Tunguska event, which took place on June 30th, 1918, in eastern Russia and resulted in the flattening of 2,000 square km (770 square mi) of forest. While far less harmful than the Cretaceous–Paleogene (K–Pg) extinction event – which took place 66 million years ago and is believed to have killed the dinosaurs – Tunguska was the most harmful asteroid event in recorded history.
In many of the images snapped by Hubble, the asteroid tails appeared as white trails that look like curved streaks, an effect caused by parallax. In astronomy, parallax is an observational effect where the apparent position of an object appears to be different based on different lines of sight. Basically, as Hubble orbited around the Earth and took several images of the galaxy, the asteroids appeared to be moving relative to the background stars and galaxies.
The asteroids own motion along their orbits and other contributing factors also led to their streaked appearance. Whereas the white streaks were identified as asteroid tails, the blue streaks are distorted images of distant galaxies behind the cluster. This effect is known as gravitational lensing, where light from distant objects is warped and magnified by the presence of an intervening object.
In this case, the intervening object who’s gravitational force magnified the light of the background galaxies was Abell 370. These more distant galaxies are too distant for Hubble to see directly, hence why astronomers use the technique to study the most distant objects in the Universe. But whereas the blue streaks were expected, the white streaks caused by asteroids took scientists completely by surprise!
This year, the European Space Agency (ESA) is co-hosting a live webcast with the European Southern Observatory (ESO) with expert interviews, news on some the most recent asteroid research, and a discussion about what killed the dinosaurs. You can watch this event tomorrow starting at 13:00 CEST (11:00 UST/04:00 PST) by going to the ESA’s Asteroid Day web page.
Further Reading: ESA
Our knowledge of space is starting to match up with our ability to get out there an explore it. There are several companies working on missions and techniques to harvest minerals from asteroids. What other resources are out there that we can use?
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On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) telescope in Hawaii announced the first-ever detection of an interstellar asteroid – I/2017 U1 (aka. ‘Oumuamua). Originally mistaken for a comet, follow-up observations conducted by the European Southern Observatory (ESO) and others confirmed that ‘Oumuamua was actually a rocky body that had originated outside of our Solar System.
News of this interstellar asteroids, the first to ever be detected by astronomers, raised a lot of excitement. And according to a new study by an international pair of astronomers, ‘Oumuamua was not the Solar System’s first interstellar visitor. Whereas ‘Oumuamua was an interloper on its way to another star system, this latest object – known as Asteroid (514107) 2015 BZ509 – appears to be a long-term resident.
The study, titled “An interstellar origin for Jupiter’s retrograde co-orbital asteroid“, recently appeared in the Monthly Notices of Royal Astronomical Society: Letters. The study team consisted of Fathi Namouni, a researcher at Maria Helena Moreira Morais, a researcher from the
After locating this asteroid, the team noticed something very interesting about it. All planets in our Solar System, and the vast majority of objects as well, orbit the Sun in the same direction. However, upon observing 2015 BZ509, the team concluded that it had a retrograde orbit – i.e. it rotated in the opposite direction as the other planets and objects. As Dr. Fathi Namouni, the lead author of the study, explained:
“How the asteroid came to move in this way while sharing Jupiter’s orbit has until now been a mystery. If 2015 BZ509 were a native of our system, it should have had the same original direction as all of the other planets and asteroids, inherited from the cloud of gas and dust that formed them.”
Using a high-resolution statistical search for stable orbits, the team found that 2015 BZ509 has been in its current orbital state since the formation of the Solar System – ca. 4.5 billion years ago. From this, they determined that the asteroid could not be indigenous to the Solar System since it would not have been able to assume its current large-inclination orbit – not when the nearby planets had early coplanar orbits and interacted with coplanar debris.
The only conclusion they could reach from these results was that this asteroid was captured from the interstellar medium 4.5 billion years ago. As Dr. Maria Helena Moreira Morais, the second author on the paper, added:
“Asteroid immigration from other star systems occurs because the Sun initially formed in a tightly-packed star cluster, where every star had its own system of planets and asteroids. The close proximity of the stars, aided by the gravitational forces of the planets, help these systems attract, remove and capture asteroids from one another.”
The discovery of the first interstellar asteroid was certainly excited and led to multiple proposals for sending a mission to study it up close. The discovery of an interstellar asteroid that became a permanent resident in our system, however, has important implications for the study of planet formation, the evolution of the Solar System, and maybe even the origin of life itself – all of which remain open questions at this point.
Looking ahead, Dr. Namouni and Dr. Moraiswant hope to obtain more information on 2015 BZ509 so they might be able to determine exactly when it how it settled in the Solar System. In so doing, they will be able to provide clues about the Sun’s original star nursery, and about how our Early Solar System might have been enriched with components necessary for the appearance of life on Earth.
And who knows? We may soon discovery many more asteroid interlopers and long-term residents in the future. The study of these could provide even more information on the early history of our Solar System, how it interacted with neighboring systems, and how the basic ingredients for life (as we know it) came to be distributed. Perhaps the Rama enthusiasts had a point when they reminded us that the Ramans “do everything in threes”!
Further Reading: RAS, MNRAS
Another topic with plenty of updates. Since we started Astronomy Cast we’ve visited many smaller objects in the Solar System up close, from Ceres and Vesta to Pluto, not to mention a comet. What have we learned?
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What if our Solar System had another generation of planets that formed before, or alongside, the planets we have today? A new study published in Nature Communications on April 17th 2018 presents evidence that says that’s what happened. The first-generation planets, or planet, would have been destroyed during collisions in the earlier days of the Solar System and much of the debris swept up in the formation of new bodies.
This is not a new theory, but a new study brings new evidence to support it.
The evidence is in the form of a meteorite that crashed into Sudan’s Nubian Desert in 2008. The meteorite is known as 2008 TC3, or the Almahata Sitta meteorite. Inside the meteorite are tiny crystals called nanodiamonds that, according to this study, could only have formed in the high-pressure conditions within the growth of a planet. This contrasts previous thinking around these meteorites which suggests they formed as a result of powerful shockwaves created in collisions between parent bodies.
“We demonstrate that these large diamonds cannot be the result of a shock but rather of growth that has taken place within a planet.” – study co-author Philippe Gillet
Models of planetary formation show that terrestrial planets are formed by the accretion of smaller bodies into larger and larger bodies. Follow the process long enough, and you end up with planets like Earth. The smaller bodies that join together are typically between the size of the Moon and Mars. But evidence of these smaller bodies is hard to find.
One type of unique and rare meteorite, called a ureilite, could provide the evidence to back up the models, and that’s what fell to Earth in the Nubian Desert in 2008. Ureilites are thought to be the remnants of a lost planet that was formed in the first 10 million years of the Solar System, and then was destroyed in a collision.
Ureilites are different than other stony meteorites. They have a higher component of carbon than other meteorites, mostly in the form of the aforementioned nanodiamonds. Researchers from Switzerland, France and Germany examined the diamonds inside 2008 TC3 and determined that they probably formed in a small proto-planet about 4.55 billion years ago.
Philippe Gillet, one of the study’s co-authors, had this to say in an interview with Associated Press: “We demonstrate that these large diamonds cannot be the result of a shock but rather of growth that has taken place within a planet.”
According to the research presented in this paper, these nanodiamonds were formed under pressures of 200,000 bar (2.9 million psi). This means the mystery parent-planet would have to have been as big as Mercury, or even Mars.
The key to the study is the size of the nanodiamonds. The team’s results show the presence of diamond crystals as large as 100 micrometers. Though the nanodiamonds have since been segmented by a process called graphitization, the team is confident that these larger crystals are there. And they could only have been formed by static high-pressure growth in the interior of a planet. A collision shock wave couldn’t have done it.
But the parent body of the ureilite meteorite in the study would have to have been subject to collisions, otherwise where is it? In the case of this meteorite, a collision and resulting shock wave still played a role.
The study goes on to say that a collision took place some time after the parent body’s formation. And this collision would have produced the shock wave that caused the graphitization of the nanodiamonds.
The key evidence is in what are called High-Angle Annular Dark-Field (HAADF) Scanning Transmission Electron Microscopy (STEM) images, as seen above. The image is two images in one, with the one on the right being a magnification of a part of the image on the left. On the left, dotted yellow lines indicate areas of diamond crystals separate from areas of graphite. On the right is a magnification of the green square.
The inclusion trails are what’s important here. On the right, the inclusion trails are highlighted with the orange lines. They clearly indicate inclusion lines that match between adjacent diamond segments. But the inclusion lines aren’t present in the intervening graphite. In the study, the researchers say this is “undeniable morphological evidence that the inclusions existed in diamond before these were broken into smaller pieces by graphitization.”
To summarize, this supports the idea that a small planet between the size of Mercury and Mars was formed in the first 10 million years of the Solar System. Inside that body, large nanodiamonds were formed by high-pressure growth. Eventually, that parent body was involved in a collision, which produced a shock wave. The shock wave then caused the graphitization of the nanodiamonds.
It’s an intriguing piece of evidence, and fits with what we know about the formation and evolution of our Solar System.
Sources:
70,000 years ago, our keen-eyed ancestors may have noticed something in the sky: a red dwarf star that came as close as 1 light year to our Sun. They would’ve missed the red dwarf’s small, dim companion—a brown dwarf—and in any case they would’ve quickly returned to their hunting and gathering. But that star’s visit to our Solar System had an impact astronomers can still see today.
The star in question is called Scholz’s star, after astronomer Ralf-Dieter Scholz, the man who discovered it in 2013. A new study published in the Monthly Notices of the Royal Astronomical Society by astronomers at the Complutense University of Madrid, and at the University of Cambridge, shows the impact Scholz’s star had. Though the star is now almost 20 light years away, its close approach to our Sun changed the orbits of some comets and asteroids in our Solar System.
When it came to our Solar System 70,000 years ago, Scholz’s star entered the Oort Cloud. The Oort Cloud is a reservoir of mostly-icy objects that spans the range from about 0.8 to 3.2 light years from the Sun. Its visit to the Oort Cloud was first explained in a paper in 2015. This new paper follows up on that work, and shows what impact the visit had.
“Using numerical simulations, we have calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come.” – Carlos de la Fuente Marcos, Complutense University of Madrid.
In this new paper, the astronomers studied almost 340 objects in our Solar System with hyperbolic orbits, which are V-shaped rather than elliptical. Their conclusion is that a significant number of these objects had their trajectories shaped by the visit from Scholz’s star. “Using numerical simulations, we have calculated the radiants or positions in the sky from which all these hyperbolic objects seem to come,” explains Carlos de la Fuente Marcos, a co-author of the study now published in Monthly Notices of the Royal Astronomical Society. They found that there’s a cluster of these objects in the direction of the Gemini Constellation.
“In principle,” he adds, “one would expect those positions to be evenly distributed in the sky, particularly if these objects come from the Oort cloud. However, what we find is very different—a statistically significant accumulation of radiants. The pronounced over-density appears projected in the direction of the constellation of Gemini, which fits the close encounter with Scholz’s star.”
There are four ways that objects like those in the study can gain hyperbolic orbits. They might be interstellar, like the asteroid Oumuamua, meaning they gained those orbits from some cause outside our Solar System. Or, they could be natives of our Solar System, originally bound to an elliptical orbit, but cast into a hyperbolic orbit by a close encounter with one of the planets, or the Sun. For objects originally from the Oort Cloud, they could start on a hyperbolic orbit because of interactions with the galactic disc. Finally, again for objects from the Oort Cloud, they could be cast into a hyperbolic orbit by interactions with a passing star. In this study, the passing star is Scholz’s star.
The one potentially weak area of this study is pointed out by the authors themselves. As they say in their summary, “…due to their unique nature, the orbital solutions of hyperbolic minor bodies are based on relatively brief arcs of observation and this fact has an impact on their reliability. Out of 339 objects in the sample, 232 have reported uncertainties and 212 have eccentricity with statistical significance.” Translated, it means that some of the computed orbits of individual objects may have errors. But the team expects the overall conclusions of their study to be correct.
The study of minor objects with hyperbolic orbits has heated up since the interstellar asteroid Oumuamua made its visit. This new study successfully connects one population of hyperbolic objects with a pre-historic visit to our Solar System by another star. The team behind the study expects that follow up studies will confirm their results.